Polycrystalline compacts including nanoparticulate inclusions and methods of forming such compacts

ABSTRACT

Polycrystalline compacts include non-catalytic nanoparticles in interstitial spaces between interbonded grains of hard material in a polycrystalline hard material. Cutting elements and earth-boring tools include such polycrystalline compacts. Methods of forming polycrystalline compacts include sintering hard particles and non-catalytic nanoparticles to faun a polycrystalline material. Methods of forming cutting elements include infiltrating interstitial spaces between interbonded grains of hard material in a polycrystalline material with a plurality of non-catalytic nanoparticles.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/901,253, filed Oct. 8, 2010, now U.S. Pat. No. 8,496,076 issued, Jul.30, 2013, which claims the benefit of U.S. Provisional PatentApplication Ser. No. 61/252,049, filed Oct. 15, 2009, the disclosure ofeach of which is hereby incorporated herein in its entirety by thisreference.

FIELD

The present invention relates generally to polycrystalline compacts,which may be used, for example, as cutting elements for earth-boringtools, and to methods of forming such polycrystalline compacts, cuttingelements, and earth-boring tools.

BACKGROUND

Earth-boring tools for forming wellbores in subterranean earthformations generally include a plurality of cutting elements secured toa body. For example, fixed-cutter earth-boring rotary drill bits (alsoreferred to as “drag bits”) include a plurality of cutting elements thatare fixedly attached to a bit body of the drill bit. Similarly, rollercone earth-boring rotary drill bits may include cones that are mountedon bearing pins extending from legs of a bit body such that each cone iscapable of rotating about the bearing pin on which it is mounted. Aplurality of cutting elements may be mounted to each cone of the drillbit. In other words, earth-boring tools typically include a bit body towhich cutting elements are attached.

The cutting elements used in such earth-boring tools often includepolycrystalline diamond compacts (often referred to as “PDCs”), whichact as cutting faces of a polycrystalline diamond material.Polycrystalline diamond material is material that includes interbondedgrains or crystals of diamond material. In other words, polycrystallinediamond material includes direct, inter-granular bonds between thegrains or crystals of diamond material. The terms “grain” and “crystal”are used synonymously and interchangeably herein.

Polycrystalline diamond compact cutting elements are typically formed bysintering and bonding together relatively small diamond grains underconditions of high temperature and high pressure in the presence of acatalyst (e.g., cobalt, iron, nickel, or alloys and mixtures thereof) toform a layer (e.g., a compact or “table”) of polycrystalline diamondmaterial on a cutting element substrate. These processes are oftenreferred to as high temperature/high pressure (HTHP) processes. Thecutting element substrate may comprise a cermet material (i.e., aceramic-metal composite material) such as, for example, cobalt-cementedtungsten carbide. In such instances, the cobalt (or other catalystmaterial) in the cutting element substrate may be swept into the diamondgrains during sintering and serve as the catalyst material for formingthe inter-granular diamond-to-diamond bonds, and the resulting diamondtable, from the diamond grains. In other methods, powdered catalystmaterial may be mixed with the diamond grains prior to sintering thegrains together in an HTHP process.

Upon formation of a diamond table using an HTHP process, catalystmaterial may remain in interstitial spaces between the grains of diamondin the resulting polycrystalline diamond compact. The presence of thecatalyst material in the diamond table may contribute to thermal damagein the diamond table when the cutting element is heated during use, dueto friction at the contact point between the cutting element and theformation.

Polycrystalline diamond compact cutting elements in which the catalystmaterial remains in the polycrystalline diamond compact are generallythermally stable up to a temperature of about seven hundred fiftydegrees Celsius (750° C.), although internal stress within the cuttingelement may begin to develop at temperatures exceeding about threehundred fifty degrees Celsius (350° C.). This internal stress is atleast partially due to differences in the rates of thermal expansionbetween the diamond table and the cutting element substrate to which itis bonded. This differential in thermal expansion rates may result inrelatively large compressive and tensile stresses at the interfacebetween the diamond table and the substrate, and may cause the diamondtable to delaminate from the substrate. At temperatures of about sevenhundred fifty degrees Celsius (750° C.) and above, stresses within thediamond table itself may increase significantly due to differences inthe coefficients of thermal expansion of the diamond material and thecatalyst material within the diamond table. For example, cobaltthermally expands significantly faster than diamond, which may causecracks to form and propagate within the diamond table, eventuallyleading to deterioration of the diamond table and ineffectiveness of thecutting element.

Furthermore, at temperatures at or above about seven hundred fiftydegrees Celsius (750° C.), some of the diamond crystals within thepolycrystalline diamond compact may react with the catalyst materialcausing the diamond crystals to undergo a chemical breakdown orback-conversion to another allotrope of carbon or another carbon-basedmaterial. For example, the diamond crystals may graphitize at thediamond crystal boundaries, which may substantially weaken the diamondtable. In addition, at extremely high temperatures, in addition tographite, some of the diamond crystals may be converted to carbonmonoxide and carbon dioxide.

In order to reduce the problems associated with differential rates ofthermal expansion and chemical breakdown of the diamond crystals inpolycrystalline diamond compact cutting elements, so-called “thermallystable” polycrystalline diamond compacts (which are also known asthermally stable products, or “TSPS”) have been developed. Such athermally stable polycrystalline diamond compact may be formed byleaching the catalyst material (e.g., cobalt) out from interstitialspaces between the interbonded diamond crystals in the diamond tableusing, for example, an acid or combination of acids (e.g., aqua regia).Substantially all of the catalyst material may be removed from thediamond table, or catalyst material may be removed from only a portionthereof. Thermally stable polycrystalline diamond compacts in whichsubstantially all catalyst material has been leached out from thediamond table have been reported to be thermally stable up totemperatures of about twelve hundred degrees Celsius (1,200° C.). It hasalso been reported, however, that such fully leached diamond tables arerelatively more brittle and vulnerable to shear, compressive, andtensile stresses than are non-leached diamond tables. In addition, it isdifficult to secure a completely leached diamond table to a supportingsubstrate. In an effort to provide cutting elements havingpolycrystalline diamond compacts that are more thermally stable relativeto non-leached polycrystalline diamond compacts, but that are alsorelatively less brittle and vulnerable to shear, compressive, andtensile stresses relative to fully leached diamond tables, cuttingelements have been provided that include a diamond table in which thecatalyst material has been leached from a portion or portions of thediamond table. For example, it is known to leach catalyst material froma cutting face, from the side of the diamond table, or both, to adesired depth within the diamond table, but without leaching all of thecatalyst material out from the diamond table.

BRIEF SUMMARY

In some embodiments, the present invention includes polycrystallinecompacts that comprise a plurality of grains of hard material that areinterbonded to form a polycrystalline hard material, and a plurality ofnon-catalytic nanoparticles disposed in interstitial spaces between thegrains of hard material.

In additional embodiments, the present invention includes cuttingelements comprising at least one such polycrystalline compact.

In additional embodiments, the present invention includes earth-boringtools that include a body, and at least one such polycrystalline compactcarried by the body.

In further embodiments, the present invention includes methods offorming polycrystalline compacts, in which a plurality of hard particlesand a plurality of non-catalytic nanoparticles are sintered to form apolycrystalline hard material comprising a plurality of interbondedgrains of hard material.

In additional embodiments, the present invention includes methods offorming cutting elements in which interstitial spaces betweeninterbonded grains of hard material in a polycrystalline material areinfiltrated with a plurality of non-catalytic nanoparticles.

BRIEF DESCRIPTION OF THE DRAWINGS

While the specification concludes with claims particularly pointing outand distinctly claiming what are regarded as embodiments of the presentinvention, various features and advantages of embodiments of theinvention may be more readily ascertained from the following descriptionof some embodiments of the invention when read in conjunction with theaccompanying drawings, in which:

FIG. 1A is a partial cut-away perspective view illustrating anembodiment of a cutting element comprising a polycrystalline compact ofthe present invention;

FIG. 1B is a simplified drawing showing how a microstructure of thepolycrystalline compact of FIG. 1A may appear under magnification, andillustrates interbonded and interspersed larger and smaller grains ofhard material;

FIG. 2 includes an enlarged view of a portion of FIG. 1B, as well assimplified diagrams illustrating different types of nanoparticles thatmay be used in fabricating a polycrystalline compact like that shown inFIGS. 1A and 1B; and

FIG. 3 is a perspective view of an embodiment of a fixed-cutterearth-boring rotary drill bit that includes a plurality ofpolycrystalline compacts like that shown in FIGS. 1A and 1B carried by abody of the drill bit.

DETAILED DESCRIPTION

The illustrations presented herein are not actual views of anyparticular polycrystalline compact, microstructure of a polycrystallinecompact, particle, cutting element, or drill bit, and are not drawn toscale, but are merely idealized representations employed to describe thepresent invention. Additionally, elements common between figures mayretain the same numerical designation.

As used herein, the term “drill bit” means and includes any type of bitor tool used for drilling during the formation or enlargement of awellbore and includes, for example, rotary drill bits, percussion bits,core bits, eccentric bits, bi-center bits, reamers, mills, drag bits,roller cone bits, hybrid bits and other drilling bits and tools known inthe art.

As used herein, the term “nanoparticle” means and includes any particlehaving an average particle diameter of about 500 nm or less.

As used herein, the term “polycrystalline material” means and includesany material comprising a plurality of grains or crystals of thematerial, which grains are bonded directly together by inter-granularbonds. The crystal structures of the individual grains of the materialmay be randomly oriented in space within the polycrystalline material.

As used herein, the term “polycrystalline compact” means and includesany structure comprising a polycrystalline material formed by a processthat involves application of pressure (e.g., compaction) to theprecursor material or materials used to form the polycrystallinematerial.

As used herein, the term “inter-granular bond” means and includes anydirect atomic bond (e.g., covalent, metallic, etc.) between atoms inadjacent grains of material.

As used herein, the term “catalyst material” refers to any material thatis capable of substantially catalyzing the formation of inter-granularbonds between grains of hard material during an HTHP process. Forexample, catalyst materials for diamond include cobalt, iron, nickel,other elements from Group VIIIA of the Periodic Table of the Elements,and alloys thereof.

As used herein, the term “non-catalytic material” refers to any materialthat is not a catalyst material.

As used herein, the term “non-catalytic nanoparticle” means and includesany nanoparticle that is not comprised of a catalytic material, diamond,or cubic boron nitride. Non-catalytic nanoparticles, in someembodiments, may comprise materials that are not any type of hardmaterial, as defined below.

As used herein, the term “hard material” means and includes any materialhaving a Knoop hardness value of about 2,000 Kg_(f)/mm² (20 GPa) ormore. In some embodiments, the hard materials employed herein may have aKnoop hardness value of about 3,000 Kg_(f)/mm² (29.4 GPa) or more. Suchmaterials include, for example, diamond and cubic boron nitride.

FIG. 1A is a simplified, partially cut-away perspective view of anembodiment of a cutting element 10 of the present invention. The cuttingelement 10 comprises a polycrystalline compact in the form of a layer ofhard polycrystalline material 12, also known in the art as apolycrystalline table, that is provided on (e.g., formed on or attachedto) a supporting substrate 16 with an interface 14 therebetween. Thoughthe cutting element 10 in the embodiment depicted in FIG. 1A iscylindrical or disc-shaped, in other embodiments, the cutting element 10may have any desirable shape, such as a dome, cone, chisel, etc.

In some embodiments, the polycrystalline material 12 comprisespolycrystalline diamond. In such embodiments, the cutting element 10 maybe referred to as a polycrystalline diamond compact (PDC) cuttingelement. In other embodiments, the polycrystalline material 12 maycomprise another hard material such as, for example, polycrystallinecubic boron nitride.

FIG. 1B is an enlarged view illustrating how a microstructure of thepolycrystalline material 12 of the cutting element 10 of FIG. 1A mayappear under magnification. As discussed in further detail below, thepolycrystalline material 12 includes interbonded grains 18 of hardmaterial. The polycrystalline material 12 also includes nanoparticlesdisposed in interstitial spaces 22 between the interbonded grains 18 ofhard material. These nanoparticulate inclusions in the polycrystallinematerial 12 may reduce an amount of catalyst material remaining in thepolycrystalline material 12 after a catalyst material is used tocatalyze formation of the polycrystalline material 12 in a sinteringprocess, such as a high temperature, high pressure (HTHP) process. Inother words, at least substantially non-catalytic nanoparticulateinclusions (i.e., nanoparticles) may be incorporated into thepolycrystalline material 12 such that the amount of catalyst materialremaining in interstitial spaces 22 between the interbonded grains 18 ofhard material in the microstructure after the sintering process isreduced by volumetric exclusion based on the presence of thenon-catalyst nanoparticles. The spatial volume occupied by thesenanoparticulates cannot be occupied by catalyst material, and, hence,the amount of catalyst material in the polycrystalline material 12 isreduced. The overall reduction of catalytic material in the grainboundary regions between the interbonded grains 18 of hard material maylead to an increase in thermal stability of the cutting element 10 byhaving a reduced coefficient of thermal expansion mismatch effect fromthe reduced content of catalyst material. Furthermore, in embodiments inwhich the hard material comprises diamond, the reduction of catalyticmaterial in between the interbonded grains 18 of hard material may alsodecrease the susceptibility of the diamond to graphitize (often referredto as “reverse graphitization”) for substantially the same reasons.

The nanoparticles disposed in the interstitial spaces 22 between theinterbonded grains 18 of hard material may comprise a non-catalyticmaterial. The non-catalytic material of the nanoparticles may comprise,for example, one or more of elementary metals (e.g., commercially puretungsten), metal alloys (e.g., tungsten alloys), intermetalliccompounds, ceramics (e.g., carbides, nitrides, oxides), and combinationsthereof As particular non-limiting examples, the non-catalyticnanoparticles may comprise carbides, nitrides, or carbonitrides ofrefractory metals such as hafnium, vanadium, molybdenum, tungsten,niobium, and titanium.

As shown in FIG. 1B, the grains 18 of the polycrystalline material 12optionally may have a multi-modal (e.g., bi-modal, tri-modal, etc.)grain size distribution. In some embodiments, the polycrystallinematerial 12 may comprise a multi-modal grain size distribution asdisclosed in at least one of Provisional U.S. patent application Ser.No. 61/232,265, which was filed on Aug. 7, 2009, and titled“Polycrystalline Compacts Including In-Situ Nucleated Grains,Earth-Boring Tools Including Such Compacts, and Methods of Forming SuchCompacts and Tools,” and U.S. patent application Ser. No. 12/558,184,which was filed on Sep. 11, 2009, and titled “Polycrystalline CompactsHaving Material Disposed in Interstitial Spaces Therein, CuttingElements and Earth-Boring Tools Including Such Compacts, and Methods ofForming Such Compacts,” the disclosures of each of which areincorporated herein in its entirety by this reference.

For example, the layer of hard polycrystalline material 12 may include afirst plurality of grains 18 of hard material having a first averagegrain size, and at least a second plurality of grains 18 of hardmaterial having a second average grain size that differs from the firstaverage grain size of the first plurality of grains 18. The secondplurality of grains 18 may be larger than the first plurality of grains18. For example, the average grain size of the larger grains 18 may beat least about one hundred fifty (150) times greater than the averagegrain size of the smaller grains 18. In additional embodiments, theaverage grain size of the larger grains 18 may be at least about fivehundred (500) times greater than the average grain size of the smallergrains 18. In yet further embodiments, the average grain size of thelarger grains 18 may be at least about seven hundred fifty (750) timesgreater than the average grain size of the smaller grains 18. Thesmaller grains 18 and the larger grains 18 may be interspersed andinterbonded to form the layer of hard polycrystalline material 12. Inother words, in embodiments in which the polycrystalline material 12comprises polycrystalline diamond, the smaller grains 18 and the largergrains 18 may be mixed together and bonded directly to one another byinter-granular diamond-to-diamond bonds 26 (represented by dashed linesin FIG. 1B).

As known in the art, the average grain size of grains within amicrostructure may be determined by measuring grains of themicrostructure under magnification. For example, a scanning electronmicroscope (SEM), a field emission scanning electron microscope (FESEM),or a transmission electron microscope (TEM) may be used to view or imagea surface of a polycrystalline material 12 (e.g., a polished and etchedsurface of the polycrystalline material 12). Commercially availablevision systems are often used with such microscopy systems, and thesevision systems are capable of measuring the average grain size of grainswithin a microstructure.

By way of example and not limitation, in embodiments in which theaverage grain size of the smaller grains 18 is between about onenanometer (1 nm) and about one hundred fifty nanometers (150 nm), theaverage grain size of the larger grains 18 may be between about fivemicrons (5 μm) and about forty microns (40 μm). Thus, in someembodiments, the ratio of the average grain size of the larger grains 18to the average grain size of the smaller grains 18 may be between about33:1 and about 40,000:1.

The large difference in the average grain size between the smallergrains 18 and the larger grains 18 may result in smaller interstitialspaces 22 or voids (represented as shaded areas in FIG. 1B) within themicrostructure of the polycrystalline material 12 (relative toconventional polycrystalline materials), and the total volume of theinterstitial spaces 22 or voids may be more evenly distributedthroughout the microstructure of the polycrystalline material 12. As aresult, any material present within the interstitial spaces 22 (e.g., acarbon compound or a catalyst material, as described below) may also bemore evenly distributed throughout the microstructure of thepolycrystalline material 12 within the relatively smaller interstitialspaces 22 therein.

In some embodiments, the number of smaller grains 18 per unit volume ofthe polycrystalline material 12 may be higher than the number of largergrains 18 per unit volume of the polycrystalline material 12.

The smaller grains 18 may comprise between about one-half of one percent(0.5%) and about thirty percent (30%) by volume of the polycrystallinematerial 12. More specifically, the smaller grains 18 may comprisebetween about one-half of one percent (0.5%) and about ten percent (10%)by volume of the polycrystalline material 12, or even between aboutone-half of one percent (0.5%) and about five percent (5%) by volume ofthe polycrystalline material 12. The remainder of the volume of thepolycrystalline material 12 may be substantially comprised by the largergrains 18. A relatively small percentage of the remainder of the volumeof the polycrystalline material 12 (e.g., less than about ten percent(10%)) may comprise interstitial spaces 22 between the smaller grains 18and the larger grains 18 of hard material.

In some embodiments, the smaller grains 18 may comprise in-situnucleated grains 18 of hard material, as disclosed in the aforementionedprovisional U.S. patent application Ser. No. 61/232,265, which was filedon Aug. 7, 2009.

The interstitial spaces 22 between the grains 18 of hard material may beat least partially filled with non-catalytic nanoparticles and with acatalyst material.

The non-catalytic nanoparticle inclusions in the polycrystallinematerial 12 may exhibit one or more of the following characteristics.

The nanoparticle inclusions may have an average major axis length belowfive hundred nanometers (500 nm).

The chemical composition of the non-catalytic nanoparticle inclusionsmay be selected such that they do not degrade, suppress, or otherwiseadversely affect the sintering of the grains 18 of hard material duringa sintering process (e.g., an HTHP process) used to form thepolycrystalline material 12 (although they may, in some embodiments,control or prevent abnormal grain growth of the grains 18).

The chemical composition of the non-catalytic nanoparticle inclusionsmay be selected such that they do not catalyze degradation of the hardmaterial after the sintering process (e.g., an HTHP process) used toform the polycrystalline material 12, or contribute to any increase incatalytic activity within the polycrystalline material 12 after thesintering process. In some embodiments, the nanoparticle inclusions mayeffectively reduce the catalytic activity within the polycrystallinematerial 12 after the sintering process. In other words, for example, ifthe polycrystalline material 12 comprises polycrystalline diamond, thenanoparticle inclusions may effectively reduce the susceptibility of thepolycrystalline diamond to reverse graphitization.

The non-catalytic nanoparticle inclusions may be functionalized tofacilitate their inclusion with the grains 18 of hard material. In otherwords, exterior surfaces of the non-catalytic nanoparticles may be atleast partially coated with a substance (e.g., an organic material) thatfacilitates controlled distribution of the nanoparticles with the matrixgrains of hard materials during pre-sintering processing, and may alsopromote adhesion of the nanoparticles to the grains 18 of hard material.Furthermore, the materials used to functionalize one or more of thenon-catalytic nanoparticles, particles of hard material, and particlesof catalyst material may be modified during processing in any desirablemanner by, for example, changing or removing functional groups in themolecules of the functionalizing material. As non-limiting examples, insome embodiments, the non-catalytic nanoparticles may be functionalizedas described in provisional U.S. patent application Ser. No. 61/324,142,filed Apr. 14, 2010 and entitled Method of Preparing PolycrystallineDiamond from Derivatized Nanodiamond, the disclosure of which isincorporated herein in its entirety by this reference.

FIG. 2 includes an enlarged view of a portion of FIG. 1B, as well assimplified diagrams illustrating different types of non-catalyticnanoparticles that may be included in the polycrystalline material 12within the interstitial spaces 22 between the grains 18 of hardmaterial.

As shown in FIG. 2, in some embodiments, the non-catalytic nanoparticlesmay comprise generally spherical nanoparticles 20A, generallydisc-shaped or platelet-shaped nanoparticles 20B (which may be round ornon-round), whisker or fiber nanoparticles 20C, or a combination of oneor more such nanoparticles.

The volume occupied by the non-catalytic nanoparticles in thepolycrystalline material 12 may be in a range extending from about 0.01%to about 50% of the volume occupied by the grains 18 of hard material inthe polycrystalline material 12.

Some of the non-catalytic nanoparticles may be mechanically bonded tothe grains 18 of hard material after the sintering process (e.g., anHPHT process) used to form the polycrystalline material 12.

In some embodiments, the polycrystalline material 12 may also include acatalyst material 24 disposed in interstitial spaces 22 between theinterbonded grains 18 of the polycrystalline hard material. The catalystmaterial 24 may comprise a catalyst used to catalyze the formation ofthe inter-granular bonds 26 between the grains of the smaller grains 18and the larger grains 18 of the polycrystalline material 12. In otherembodiments, however, the interstitial spaces 22 between the grains 18in some, or all regions of the polycrystalline material 12 may be atleast substantially free of such a catalyst material 24. In suchembodiments, the interstitial spaces 22 may comprise voids filled withgas (e.g., air), in addition to any non-catalytic nanoparticles presenttherein.

In embodiments in which the polycrystalline material 12 comprisespolycrystalline diamond, the catalyst material 24 may comprise a GroupVIIIA element (e.g., iron, cobalt, or nickel) or an alloy thereof, andthe catalyst material 24 may comprise between about one-half of onepercent (0.1%) and about ten percent (10%) by volume of the hardpolycrystalline material 12. In additional embodiments, the catalystmaterial 24 may comprise a carbonate material such as, for example, acarbonate of one or more of magnesium, calcium, strontium, and barium.Carbonates may also be used to catalyze the formation of polycrystallinediamond.

The layer of hard polycrystalline material 12 of the cutting element 10may be formed using a high temperature/high pressure (HTHP) process.Such processes, and systems for carrying out such processes, aregenerally known in the art. In some embodiments, the polycrystallinematerial 12 may be formed on a supporting substrate 16 (as shown in FIG.1A) of cemented tungsten carbide or another suitable substrate materialin a conventional HTHP process of the type described, by way ofnon-limiting example, in U.S. Pat. No. 3,745,623 to Wentorf et al.(issued Jul. 17, 1973), or may be formed as a freestandingpolycrystalline material 12 (i.e., without the supporting substrate 16)in a similar conventional HTHP process as described, by way ofnon-limiting example, in U.S. Pat. No. 5,127,923 to Bunting et al.(issued Jul. 7, 1992), the disclosure of each of which patents isincorporated herein in its entirety by this reference. In someembodiments, the catalyst material 24 may be supplied from thesupporting substrate 16 during an HTHP process used to form thepolycrystalline material 12. For example, the substrate 16 may comprisea cobalt-cemented tungsten carbide material. The cobalt of thecobalt-cemented tungsten carbide may serve as the catalyst material 24during the HTHP process. Furthermore, in some embodiments, thenon-catalytic nanoparticles also may be supplied from the supportingsubstrate 16 during an HTHP process used to form the polycrystallinematerial 12. For example, the substrate 16 may comprise acobalt-cemented tungsten carbide material that also includesnon-catalytic nanoparticles therein. The cobalt and the non-catalyticnanoparticles of the substrate 16 may sweep into the hard materialgrains 18 process.

To form the polycrystalline material 12 in an HTHP process, aparticulate mixture comprising particles (e.g., grains) of hard materialand non-catalytic nanoparticles may be subjected to elevatedtemperatures (e.g., temperatures greater than about one thousand degreesCelsius (1,000° C.)) and elevated pressures (e.g., pressures greaterthan about five gigapascals (5.0 GPa)) to form inter-granular bonds 26(FIG. 1B) between the particles of hard material, thereby forming theinterbonded grains 18 of the hard polycrystalline material 12. In someembodiments, the particulate mixture may be subjected to a pressuregreater than about six gigapascals (6.0 GPa) and a temperature greaterthan about one thousand and five hundred degrees Celsius (1,500° C.) inthe HTHP process.

The time at the elevated temperatures and pressures may be relativelyshort when compared to conventional HTHP processes to prevent the atomsof the smaller grains 18 from diffusing to, and being incorporated into,the larger grains 18. For example, in some embodiments, the particulatemixture may be subjected to a pressure greater than about sixgigapascals (6.0 GPa) and a temperature greater than about one thousandand five hundred degrees Celsius (1,500° C.) for less than about twominutes (2.0 min.) during the HTHP process.

In embodiments in which a carbonate catalyst material 24 (e.g., acarbonate of one or more of magnesium, calcium, strontium, and barium)is used to catalyze the formation of polycrystalline diamond, theparticulate mixture may be subjected to a pressure greater than aboutseven point seven gigapascals (7.7 GPa) and a temperature greater thanabout two thousand degrees Celsius (2,000° C.).

The particulate mixture may comprise hard particles for forming thegrains 18 of hard material previously described herein. The particulatemixture may also comprise at least one of particles of catalyst material24, and non-catalytic nanoparticles. In some embodiments, theparticulate mixture may comprise a powder-like substance. In otherembodiments, however, the particulate mixture may be carried by (e.g.,on or in) another material, such as a paper or film, which may besubjected to the HTHP process. An organic binder material also may beincluded with the particulate mixture to facilitate processing.

Thus, in some embodiments, the non-catalytic nanoparticles may beadmixed with the hard particles used to form the grains 18 to form aparticulate mixture, which then may be sintered in an HPHT process.

In some embodiments, the non-catalytic nanoparticles may be admixed withthe hard particles used to form the grains 18 of hard material prior toa modified HPHT sintering process used to synthesize a nanoparticulatecomposite that includes the non-catalytic nanoparticles andnanoparticles of hard material.

In some embodiments, the non-catalytic nanoparticles may be grown on,attached, adhered, or otherwise connected to the hard particles used toform the grains 18 prior to the sintering process. The non-catalyticnanoparticles may be attached to the hard particles by functionalizingexterior surfaces of at least one of the non-catalytic nanoparticles andthe hard particles. After attaching the non-catalytic nanoparticles tothe hard particles, the resulting particulate mixture may be subjectedto an HPHT process to form a polycrystalline material 12, as describedabove.

In additional embodiments, the non-catalytic nanoparticles may becombined with the catalyst material prior to the sintering process. Forexample, the non-catalytic nanoparticles may be grown on, attached,adhered, or otherwise connected to particles of catalyst material (whichparticles of catalyst material may also be or include nanoparticles ofcatalyst material in some embodiments of the invention), and the coatedparticles of catalyst material may be combined with hard particles toform the particulate mixture prior to the sintering process. Thenon-catalytic nanoparticles may be attached to the particles of catalystmaterial by functionalizing exterior surfaces of at least one of thenon-catalytic nanoparticles and the catalyst particles. After attachingthe non-catalytic nanoparticles to the catalyst particles and admixingwith hard particles, the resulting particulate mixture may be subjectedto an HPHT process to form a polycrystalline material 12, as describedabove.

In some embodiments, the non-catalytic nanoparticles may be grown on,attached, adhered, or otherwise connected to both particles of hardmaterial and particles of catalyst material, and the coated particlesmay be combined to form the particulate mixture.

As previously mentioned, a particulate mixture that includes hardparticles for forming the interbonded grains 18 of hard material, and,optionally, non-catalytic nanoparticles and/or a catalyst material 24(for catalyzing the formation of inter-granular bonds 26 between thesmaller grains 18 and the larger grains 18), may be subjected to an HTHPprocess to form a polycrystalline material 12. As non-limiting examples,the particulate mixture may comprise a mixture as described in, and maybe formed by the processes described in, the aforementioned provisionalU.S. patent application Ser. No. 61/324,142, filed Apr. 14, 2010 andentitled Method of Preparing Polycrystalline Diamond from DerivatizedNanodiamond. After the HTHP process, catalyst material 24 (e.g., cobalt)and non-catalytic nanoparticles may be disposed in at least some of theinterstitial spaces 22 between the interbonded smaller grains 18 andlarger grains 18.

Optionally, the catalyst material 24, the non-catalytic nanoparticles,or both the catalyst material 24 and the non-catalytic nanoparticles maybe removed from the polycrystalline material 12 after the HTHP processusing processes known in the art. For example, a leaching process may beused to remove the catalyst material 24 and/or the non-catalyticnanoparticles from the interstitial spaces 22 between the grains 18 ofhard material. By way of example and not limitation, the polycrystallinematerial 12 may be leached using a leaching agent and process such asthose described more fully in, for example, U.S. Pat. No. 5,127,923 toBunting et al. (issued Jul. 7, 1992), and U.S. Pat. No. 4,224,380 toBovenkerk et al. (issued Sep. 23, 1980), the disclosure of each of whichpatent is incorporated herein in its entirety by this reference.Specifically, aqua regia (a mixture of concentrated nitric acid (HNO₃)and concentrated hydrochloric acid (HCl)) may be used to at leastsubstantially remove catalyst material 24 and/or non-catalyticnanoparticles from the interstitial spaces 22. It is also known to useboiling hydrochloric acid (HCl) and boiling hydrofluoric acid (HF) asleaching agents. One particularly suitable leaching agent ishydrochloric acid (HCl) at a temperature of above one hundred tendegrees Celsius (110° C.), which may be provided in contact with thepolycrystalline material 12 for a period of about two (2) hours to aboutsixty (60) hours, depending upon the size of the body of polycrystallinematerial 12. After leaching the polycrystalline material 12, theinterstitial spaces 22 between the interbonded smaller grains 18 andlarger grains 18 of hard material within the polycrystalline material 12subjected to the leaching process may be at least substantially free ofcatalyst material 24 used to catalyze formation of inter-granular bonds26 between the grains 18 in the polycrystalline material 12, and may beat least substantially free of non-catalytic nanoparticles. Furthermore,only a portion of the polycrystalline material 12 may be subjected tothe leaching process, or the entire body of the polycrystalline material12 may be subjected to the leaching process.

In additional embodiments of the present invention, non-catalyticnanoparticles may be introduced into the interstitial spaces 22 betweeninterbonded grains 18 of hard, polycrystalline material 12 aftercatalyst material 24 and any other material in the interstitial spaces22 has been removed from the interstitial spaces 22 (e.g., by a leachingprocess). For example, after subjecting a polycrystalline material 12 toa leaching process, non-catalytic nanoparticles may be introduced intothe interstitial spaces 22 between the grains 18 of hard material in thepolycrystalline material 12. Non-catalytic nanoparticles may besuspended in a liquid (e.g., water or another polar solvent) to form asuspension, and the leached polycrystalline material 12 may be soaked inthe suspension to allow the liquid and the non-catalytic nanoparticlesto infiltrate into the interstitial spaces 22. The liquid (and thenon-catalytic nanoparticles suspended therein) may be drawn into theinterstitial spaces 22 by capillary forces. In some embodiments,pressure may be applied to the liquid to facilitate infiltration of theliquid suspension into the interstitial spaces 22.

After infiltrating the interstitial spaces 22 with the liquidsuspension, the polycrystalline material 12 may be dried to remove theliquid from the interstitial spaces 22, leaving behind the non-catalyticnanoparticles therein. Optionally, a thermal treatment process may beused to facilitate the drying process.

The polycrystalline material 12 then may be subjected to a thermalprocess (e.g., a standard vacuum furnace sintering process) to at leastpartially sinter the non-catalytic nanoparticles within the interstitialspaces 22 in the polycrystalline material 12. Such a process may becarried out below any temperature that might be detrimental to thepolycrystalline material 12.

Embodiments of cutting elements 10 of the present invention that includea polycrystalline compact comprising polycrystalline material 12 formedas previously described herein, such as the cutting element 10illustrated in FIG. 1A, may be formed and secured to an earth-boringtool such as, for example, a rotary drill bit, a percussion bit, acoring bit, an eccentric bit, a reamer tool, a milling tool, etc., foruse in forming wellbores in subterranean formations. As a non-limitingexample, FIG. 3 illustrates a fixed-cutter type earth-boring rotarydrill bit 36 that includes a plurality of cutting elements 10, each ofwhich includes a polycrystalline compact comprising polycrystallinematerial 12 as previously described herein. The rotary drill bit 36includes a bit body 38, and the cutting elements 10, which includepolycrystalline compacts 12, are carried by (e.g., bonded to) the bitbody 38. The cutting elements 10 may be brazed (or otherwise secured)within pockets formed in the outer surface of the bit body 38.

Polycrystalline hard materials that include non-catalytic nanoparticlesin interstitial spaces between the interbonded grains of hard material,as described hereinabove, may exhibit improved thermal stability,improved mechanical durability, or both improved thermal stability andimproved mechanical durability relative to previously knownpolycrystalline hard materials. By including the non-catalyticnanoparticles in the interstitial spaces between the interbonded grainsof hard material, less catalyst material may be disposed in interstitialspaces between the grains in the ultimate polycrystalline hard material,which may improve one or both of the thermal stability and themechanical durability of the polycrystalline hard material.

Additional non-limiting example embodiments of the invention aredescribed below.

Embodiment 1: A polycrystalline compact, comprising: a plurality ofgrains of hard material, the plurality of grains of hard material beinginterbonded to form a polycrystalline hard material; and a plurality ofnon-catalytic nanoparticles disposed in interstitial spaces between thegrains of hard material.

Embodiment 2: The polycrystalline compact of Embodiment 1, wherein theplurality of grains of hard material comprises grains of diamond.

Embodiment 3: The polycrystalline compact of Embodiment 1 or Embodiment2, wherein the nanoparticles of the plurality of non-catalyticnanoparticles comprise at least one of a metal, a metal alloy, anintermetallic compound, and a ceramic.

Embodiment 4: The polycrystalline compact of any one of Embodiments 1through 3, wherein the nanoparticles of the plurality of non-catalyticnanoparticles comprise at least one of a carbide, a nitride, and anoxide.

Embodiment 5: The polycrystalline compact of any one of Embodiments 1through 4, further comprising a catalyst material in the interstitialspaces between the grains of hard material.

Embodiment 6: The polycrystalline compact of any one of Embodiment 1through 5, wherein the plurality of grains of hard material comprises: aplurality of smaller grains of hard material having a first averagegrain size; and a plurality of larger grains of hard material having asecond average grain size that is at least about one hundred fifty (150)times larger than the first average grain size.

Embodiment 7: The polycrystalline compact of Embodiment 6, wherein thesecond average grain size is between two hundred fifty (250) times andseven hundred fifty (750) times larger than the first average grainsize.

Embodiment 8: The polycrystalline compact of Embodiment 6 or Embodiment7, wherein the first average grain size is between about one nanometer(1 nm) and about one hundred fifty nanometers (150 nm), and the secondaverage grain size is between about five microns (5 μm) and about fortymicrons (40 μm).

Embodiment 9: The polycrystalline compact of any one of Embodiments 1through 8, wherein a total volume occupied by the plurality ofnon-catalytic nanoparticles in the polycrystalline hard material is in arange extending from about 0.01% to about 50% of a total volume occupiedby the grains of hard material in the polycrystalline hard material.

Embodiment 10: A cutting element, comprising: a substrate; and apolycrystalline compact as recited in any one of Embodiments 1 through 9on the substrate.

Embodiment 11: An earth-boring tool comprising a body and apolycrystalline compact as recited in any one of Embodiments 1 through 9carried by the body.

Embodiment 12: The earth-boring tool of Embodiment 11, wherein theearth-boring tool is a fixed-cutter rotary drill bit.

Embodiment 13: A method of forming a polycrystalline compact, comprisingsintering a plurality of hard particles and a plurality of non-catalyticnanoparticles to form a polycrystalline hard material comprising aplurality of interbonded grains of hard material.

Embodiment 14: The method of Embodiment 13, further comprising selectingthe hard particles of the plurality of hard particles to comprisediamond.

Embodiment 15: The method of Embodiment 13 or Embodiment 14, furthercomprising selecting the nanoparticles of the plurality of non-catalyticnanoparticles to comprise at least one of a metal, a metal alloy, anintermetallic compound, and a ceramic.

Embodiment 16: The method of Embodiment 13 through 15, furthercomprising selecting the nanoparticles of the plurality of non-catalyticnanoparticles to comprise at least one of a carbide, a nitride, and anoxide.

Embodiment 17: The method of any one of Embodiment 13 through 16,further comprising catalyzing the formation of inter-granular bondsbetween the grains of hard material.

Embodiment 18: The method of any one of Embodiments 13 through 17,wherein sintering a plurality of hard particles and a plurality ofnon-catalytic nanoparticles comprises sintering the plurality of hardparticles and the plurality of non-catalytic nanoparticles in an HTHPprocess.

Embodiment 19: The method of any one of Embodiments 13 through 18,further comprising adhering the nanoparticles of the plurality ofnon-catalytic nanoparticles to exterior surfaces of the hard particlesof the plurality of hard particles prior to sintering the plurality ofhard particles and the plurality of non-catalytic nanoparticles.

Embodiment 20: The method of Embodiment 19, further comprisingfunctionalizing at least one of the plurality of hard particles and theplurality of non-catalytic nanoparticles to promote adhesion of thenanoparticles of the plurality of non-catalytic nanoparticles to theexterior surfaces of the hard particles of the plurality of hardparticles.

Embodiment 21: A method of faulting a cutting element, comprisinginfiltrating interstitial spaces between interbonded grains of hardmaterial in a polycrystalline material with a plurality of non-catalyticnanoparticles.

Embodiment 22: The method of Embodiment 21, further comprising selectingthe grains of hard material to comprise diamond grains.

Embodiment 23: The method of Embodiment 21 or Embodiment 22, furthercomprising selecting the nanoparticles of the plurality of non-catalyticnanoparticles to comprise at least one of a metal, a metal alloy, anintermetallic compound, and a ceramic.

Embodiment 24: The method of any one of Embodiments 21 through 23,further comprising selecting the nanoparticles of the plurality ofnon-catalytic nanoparticles to comprise at least one of a carbide, anitride, and an oxide.

The foregoing description is directed to particular embodiments for thepurpose of illustration and explanation. It will be apparent, however,to one skilled in the art that many modifications and changes to theembodiments set forth above are possible without departing from thescope of the embodiments disclosed herein as hereinafter claimed,including legal equivalents. It is intended that the following claims beinterpreted to embrace all such modifications and changes.

What is claimed is:
 1. A polycrystalline compact, comprising: aplurality of grains of hard material, the plurality of grains of hardmaterial being interbonded to form a polycrystalline hard material; anda plurality of generally spherical non-catalytic nanoparticles disposedin interstitial spaces between the grains of hard material, wherein thenanoparticles of the plurality comprise a material other than diamond.2. The polycrystalline compact of claim 1, wherein the plurality ofnon-catalytic nanoparticles comprises a metal.
 3. The polycrystallinecompact of claim 1, wherein the plurality of non-catalytic nanoparticlescomprises a metal alloy.
 4. The polycrystalline compact of claim 1,wherein the plurality of non-catalytic nanoparticles comprises acarbide.
 5. The polycrystalline compact of claim 1, wherein theplurality of non-catalytic nanoparticles comprises a nitride.
 6. Thepolycrystalline compact of claim 1, wherein the plurality ofnon-catalytic nanoparticles comprises an oxide.
 7. The polycrystallinecompact of claim 1, wherein the plurality of grains of hard materialcomprises grains of diamond.
 8. The polycrystalline compact of claim 1,further comprising a catalyst material in the interstitial spacesbetween the grains of hard material.
 9. The polycrystalline compact ofclaim 1, wherein the plurality of grains of hard material comprises: aplurality of smaller grains of hard material having a first averagegrain size; and a plurality of larger grains of hard material having asecond average grain size that is at least about one hundred fifty (150)times larger than the first average grain size.
 10. The polycrystallinecompact of claim 1, wherein a total volume occupied by the plurality ofnon-catalytic nanoparticles in the polycrystalline hard material is in arange extending from about 0.01% to about 50% of a total volume occupiedby the grains of hard material in the polycrystalline hard material. 11.The polycrystalline compact, comprising: a plurality of grains of hardmaterial, the plurality of grains of hard material being interbonded toform a polycrystalline hard material; and a plurality of non-cayalyticnanoparticles disposed in interstitial spaces between the grains of hardmaterial, wherein the plurality of non-catalytic nanoparticles comprisesan intermetallic compound.
 12. The polycrystalline compact of claim 11,wherein the nanoparticles of the plurality of non-catalyticnanoparticles comprise platelets or fibers.
 13. The polycrystallinecompact of claim 11, wherein the nanoparticles of the plurality ofnon-catalytic nanoparticles comprise generally spherical nanoparticles.14. A method of forming a polycrystalline compact, comprising sinteringa plurality of hard particles and a plurality of generally sphericalnon-catalytic nanoparticles to form a polycrystalline hard materialcomprising a plurality of interbonded grains of hard material, whereinthe non-catalytic nanoparticles of the plurality comprise a materialother than diamond.
 15. The method of claim 14, wherein thenon-catalytic nanoparticles of the plurality comprise a metal.
 16. Themethod of claim 14, wherein the non-catalytic nanoparticles of theplurality comprise a metal alloy.
 17. The method of claim 14, whereinthe non-catalytic nanoparticles of the plurality comprise anintermetallic compound.
 18. The method of claim 14, wherein thenon-catalytic nanoparticles of the plurality comprise a carbide.
 19. Themethod of claim 14, wherein the non-catalytic nanoparticles of theplurality comprise a nitride.
 20. The method of claim 14, wherein thenon-catalytic nanoparticles of the plurality comprise an oxide.